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  java数据库连接（jdbc）
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      <h1 id="一、jdbc概念"><a href="#一、jdbc概念" class="headerlink" title="一、jdbc概念"></a>一、jdbc概念</h1><p><strong>jdbc</strong>（Java Database Connectivity），是一种用于执行SQL语句的Java API，就是java操作数据库嘛！<br><strong>其本质是官方定义的一套操作所有关系型数据库的接口。</strong></p>
<p>常见的关系数据库有<a href="#">Oracle、DB2、Microsoft SQL Server、Microsoft Access、MySQL</a>等，而jdbc就是为这些关系型数据库提供统一访问，数据库厂商自己写的实现类，封装成数据库驱动jar包。</p>
<p><img src="https://yolin121.oss-cn-beijing.aliyuncs.com/blogimg/05190.jpg?x-oss-process=image/resize,m_fill,h_200,w_200" alt=""></p>
<h1 id="二、jdbc使用"><a href="#二、jdbc使用" class="headerlink" title="二、jdbc使用"></a>二、jdbc使用</h1><h3 id="1、导入驱动jar包"><a href="#1、导入驱动jar包" class="headerlink" title="1、导入驱动jar包"></a>1、导入驱动jar包</h3><a id="more"></a>
<p>将jar包复制到项目中  WebContent&gt;WEB-INF&gt;lib 目录下</p>
<p>jar包地址： <a href="https://ww.lanzous.com/ict2kle" target="_blank" rel="noopener">https://ww.lanzous.com/ict2kle</a></p>
<p><img src="https://yolin121.oss-cn-beijing.aliyuncs.com/blogimg/051902.png" alt=""></p>
<h3 id="2、注册驱动"><a href="#2、注册驱动" class="headerlink" title="2、注册驱动"></a>2、注册驱动</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">Class.forName(<span class="string">"com.mysql.jdbc.Driver"</span>);</span><br></pre></td></tr></table></figure>
<p> JVM 加载所需的驱动程序到内存中执行，因此它可以实现你的 JDBC 请求。</p>
<h3 id="3、获取数据库连接对象"><a href="#3、获取数据库连接对象" class="headerlink" title="3、获取数据库连接对象"></a>3、获取数据库连接对象</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">Connection conn=DriverManager.getConnection(<span class="string">"jdbc:mysql://localhost:3306/test"</span>,<span class="string">"root"</span>,<span class="string">"123"</span>);</span><br></pre></td></tr></table></figure>

<p><img src="https://yolin121.oss-cn-beijing.aliyuncs.com/blogimg/051903.png" alt=""></p>
<p>如图输出内容证明数据库连接成功</p>
<blockquote>
<p><strong>DriverManager</strong>:驱动管理对象，用于获取数据库连接，其中有三个参数</p>
</blockquote>
<ul>
<li>指定连接的路径：不同数据库语法有差异，这里以mysql为例：<br><a href="#"> jdbc:mysql://ip地址（域名）：端口号/数据库名称</a></li>
<li>数据库用户名</li>
<li>数据库密码</li>
</ul>
<h3 id="4、获取sql语句执行对象"><a href="#4、获取sql语句执行对象" class="headerlink" title="4、获取sql语句执行对象"></a>4、获取sql语句执行对象</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">Statement stat=conn.createStatement();</span><br></pre></td></tr></table></figure>
<blockquote>
<p>stat:执行sql的对象</p>
</blockquote>
<p>int executeUpdate(String sql):执行DML语句（insert、update、delete）</p>
<h3 id="5、执行sql"><a href="#5、执行sql" class="headerlink" title="5、执行sql"></a>5、执行sql</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">stat.execute(<span class="string">"insert into student values(20,'zhutongxin')"</span>);</span><br><span class="line">ResultSet res=stat.executeQuery(<span class="string">"select * from student"</span>);</span><br><span class="line"><span class="keyword">while</span>(res.next())&#123;</span><br><span class="line">			System.out.println(res.getString(<span class="number">1</span>)+<span class="string">" "</span>+res.getString(<span class="number">2</span>));</span><br><span class="line">		&#125;</span><br></pre></td></tr></table></figure>

<p><img src="https://yolin121.oss-cn-beijing.aliyuncs.com/blogimg/051904.png" alt=""></p>
<h3 id="6、释放资源"><a href="#6、释放资源" class="headerlink" title="6、释放资源"></a>6、释放资源</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">   stat.close();</span><br><span class="line">conn.close();</span><br></pre></td></tr></table></figure>
<p>就好比你借了东西用完后要归还一样，类似于io数据流，如果不释放资源，长期下去就会造成内存溢出</p>
<h1 id="三、代码"><a href="#三、代码" class="headerlink" title="三、代码"></a>三、代码</h1><p>这里只是简单的jdbc的使用，更多对数据库的操作将会在后面介绍</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> request.demo;</span><br><span class="line"><span class="keyword">import</span> java.sql.*;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">jdbcdemo1</span> </span>&#123;</span><br><span class="line">	<span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> Exception </span>&#123;</span><br><span class="line">		<span class="comment">//注册驱动</span></span><br><span class="line">		Class.forName(<span class="string">"com.mysql.jdbc.Driver"</span>);</span><br><span class="line">		<span class="comment">//获取数据库连接对象</span></span><br><span class="line">		Connection conn=DriverManager.getConnection(<span class="string">"jdbc:mysql://localhost:3306/test"</span>,<span class="string">"root"</span>,<span class="string">"123"</span>);</span><br><span class="line">		<span class="comment">//获取sql语句执行对象</span></span><br><span class="line">	<span class="comment">//	System.out.println(conn);</span></span><br><span class="line">		Statement stat=conn.createStatement();	</span><br><span class="line">		stat.execute(<span class="string">"insert into student values(20,'zhutongxin')"</span>);</span><br><span class="line">		ResultSet res=stat.executeQuery(<span class="string">"select * from student"</span>);	</span><br><span class="line">		<span class="keyword">while</span>(res.next())&#123;</span><br><span class="line">			System.out.println(res.getString(<span class="number">1</span>)+<span class="string">" "</span>+res.getString(<span class="number">2</span>));</span><br><span class="line">		&#125;</span><br><span class="line">		stat.close();</span><br><span class="line">		conn.close();</span><br><span class="line">	&#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

      
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